There are an estimated 500,000 ocular surgical procedures (eye operations) being performed annually in the U.S. These include vitrectomy, irrigation and aspiration of cataracts, and phacoemulsification. In a substantial number of these, there occurs potentially damaging stress to the lens or corneal endothelium. This may result in irreversible harm to the lens or cornea, resulting in poor vision, necessitating a second operation, or use of heavy glasses if the lens has to be removed.
For some time a variety of solutions have been used for intraocular irrigation or infusion during such clinical procedures. The effect of the composition of such solutions on the corneal endothelium.sup.1-5 and lens has been investigated..sup.3,6 There seems to be no doubt that a physiologic saline solution containing essential cations and glucose is a necessary minimum for short-term maintenance of the lens and corneal endothelial function. The use of bicarbonate as a buffer also appears helpful. The necessity for other additives such as adenosine and gluthathione in a clinically useful infusion solution has been claimed, but has yet to be proved. The instability of these compounds in solutions may offset any possible advantage.
Although physiologic solutions maintain a normal environment for a healthy corneal endothelium and lens, conditions may differ if the endothelium or lens is under stress or is diseased, a situation often encountered in diabetic patients and older individuals.
Regarding extraocular use of dextran solutions, immersion of donor corneas in five percent dextran (mw 40,000) in tissue culture, TC 199 solution, (McCarey-Kaufman or M-K media) has been shown to be more effective than conventional eye bank techniques in preserving endothelial cell viability, as measured by temperature reversal studies, electron microscopy,.sup.7,8 vital staining,.sup.9 metabolic studies,.sup.10 and corneal grafting in rabbits.sup.11 and cats..sup.12 Its clinical value in maintaining eye bank corneas prior to keratoplasty has been demonstrated..sup.13-16 Corneas stored at 4.degree. C. in this media do not swell to any great extent when compared to moist chamber-stored eyes.
However, to our present knowledge no studies have been published outside of our laboratory demonstrating the use of dextran as a component of an intraocular irrigation or infusion fluid. It is to be noted from the prior work with dextran that is was not considered for use inside an intact living eye. Further, solutions used for extraocular preservation (M-K or TC 199 solution) are complex tissue culture media containing amino acids and antibiotics. These solutions have the serious drawback of having a much greater tendency toward contamination. They are difficult to sterilize, a necessity for intraocular use, as they contain labile components, the amino acids and antibiotics. Likewise, the viscosity, toxicity, and the metabolic or excretory fate of dextran when used intraocularly was not known or predictable from such studies.
Accordingly, there is a need to provide an improved infusion and irrigation solution which can compensate for or help prevent, stress-induced lens and cornea damage during such clinical procedures as vitrectomy, irrigation and aspiration of cataracts, and phacoemulsification.